i,m going to need a good wire man for this
started up my engine last week after a complete top to botom rebuild(92 saph 4x4 with L8 ,STG 1,done all the work my self except for the rebore.and she ran first turn of the key and was spot on,no bangs,clatters,or overtemps.
but the idle speed control valve appears to be on full duty cycle when started from cold its grand but while warming up it dosent trim back so when fully warm unless i disconnect it the idle speed ends up at 2500 rpm .when its disconnected the idle speed is perfect.when the ignition is just switched on you can here a slight buzz of the valve.
secondly i cannot get the aircon to engage,the system works perfect if i manually earth the relay called "idle speed compensation relay"which appears to look for an earth through pin 12 of the ecu this relay despite its name when earthed actually supplies the live feed for the clutch on the aircon pump .are to two problems related? pin 34 is the earth for the iscv.any comments would be greatfull

 

Velocity, I have exactly the same problem (ISCV, high idle, disconnected = ok), but no air con on mine.
I have run out of ideas - would love to know what you find out...

Have you tried to clean the ISCV ? Take it out, remove the o-rings and dunk the end in petrol for a while - mine came out pristine, but still I have the high idle,

 

did the usual clean out and stuff and no joy,a few years back it used to do the same intermitantly and i would disconnect it,then reconnect back up after a maybe a week and all would be well ,but something is telling the iscv that either the engine is under load or its still cold,and i know the temp sensor is ok,the valve should modulate in opperation and it never really stays in the same spot for long,but mine is full whack open,we need the ecu guru,s

 

Likewise, checked for air-leaks and my temp sensor is new.
Is your map sensor ok ?

 

sounds like exactly what mine did.

turned out to be the ajustment of the TPS. with the ignition switched on and the cover off the ecu multiplug, go across pins 17 and 30 and you should ajust the position (via its elongated holes) until you read 0.2 - 0.25 VDC back at the ecu with a multimeter. you will need to take the intake pipe off and undoo the 4 small bolts around the tps housing to get it off and access the elongated slots for the tps.

 

Dave,

are you sure these readings are for a 4x4 ? Mine reads 4.95V or so at idle.
Only asking cos the 2wd and 4wd work in opposite ways.

Cheers

 

dave you may have hit the nail with the hammer.i had to adjust that sensor during the rebuild and was never quite happy with the readings and i was using ohms , i have different measurments for the sensor which is 0.5 to 0.6 volts with the throttle closed but i will try it at that and see what happens,
frog dave,s above settings are for the later type tps,which is my one,the earlier type has the settings in reverse according to the info i,m reading here in front of me.someone may have swapped the wires around in the ecu multyplug in you car are done something else,
will let yez know what happens

 

Thanks velocity - the wires are the correct way round, checked them from a diagram showing the relationship between the connector that plugs into the tps and the ecu connector pins.

Sounds like I should have another go at setting it up, if no luck - time for a new one then !

Good luck with yours.

 

just did a check.using the signal wire pin 17 and earth and am getting 0.68 volts at throttle close rising to 4.85 volts at full throttle so it appears to be out of tolerance in the same direction .but i see what you are saying frog as i had this delema when setting it up first using ohms as a guide as the sensor and throttle body were on the bench.i,m sure your set up is correct but it depends were you take the readings, i will re set it in the next day or so and see what happens and will post the results and procedure i used here
wish me luck

 

the readings im on about are 100% for a4x4 tps, the 2wd as u righly said are the ther way round and reads 5 volts at idle.

you will notice that when the 4x4 one is reading the correct 0.2-0.25 volts, it is almost smack in the middle of its elongated goles

 

Sorry to butt in but does that mean for a 2wd as it should read 5v at idle should it read 0.2-0.25 at full throttle then?

 

not too sure for the actual figures for the 2wd one tbh, they are opposite to the 4wd one , but i dont know whether they are exactly opposite, if u know what i mean...

 

dave you are the man ,problem sorted and even the aircon is engaging correctly
stuck a voltmeter between pin 17 and earth,was getting 0.68 volts so i moved the tps until i got 0.3 volts,then pushed to full throttle and was getting 4.55 volts so i,m happy with that
started her up and shes perfect iscv is spot on,and incidently the tps is now sitting exactly half way in its slots
frog i reckon you need to try this out,

 

Excellent news sir

When you say earth, do you mean at the battery or pin 30 of the ECU ?

 

frog i put one probe in pin 17 and earthed the other to the body of the ecu,just because it was convienant,u could use pin 1 or 19 as they are both earths.either way it worked for me the tps in the middle of the slots appears to be a good ballpark start point. let me know how you get on and we.ll try and get you sorted aswell

 

biggidy biggidy bong - good news

 

Guys, progress at last on two fronts (out of three)...

Checked TPS, it was reading very close to 0V, so adjusted back up to 0.23, idle is now 900rpm when warm

Drove the car today, and she was still mis-firing + the base idle is set too low (approx 500rpm with ISCV disconnected), so I thought I'd adjust the idle.

While doing it, and with the engine running, I could hear the amal valve clicking on and off at random, so I wiggled the wires and it clicked even more...

Had a spare which is now on the car, cross fingers that might be my misfiring sorted too

Only thing is, my base idle screw is stuck, it won't budge

 

best bet would be to remove the inlet throttle boddy and get it in a vice with saftjaws (not too tight as u may deform the ally, and leave it soaking with some plus gas or wd40 etc over night and then geta good fitting parallel blade screwdriver down th ehole and give it a whack on the end with a hammer a coupl eof times, this usually does the trick, next move woulbe be "get the gas out" geta blowlamp around the casting where the screw is and warm it up, being carefull not to melt the ally again, loads of wd40 down the hole and try again.

 

Mmmm, surgery Might try this on sunday

Thanks again Dave

 

good stuff thats good progress idle speed almost sorted and its a nice one to solve,
dave i think you have provided a solution to 90% of all idle speed control valve problems and 100% of mine,if we ever meet its pints on me

 

And three on me, cos he also helped me sort my noisy tappets out

 

Ive just done this for my 4x4 engine, after long term suffering from high idle (the ICSV has just been left unplugged).
I did also replace the TPS.
Set it as you described above, plugged the ICSV back on and it idle's perfectly for the first time.
And i did not have 0.2 volts at the ECU, so it was adjusted incorrectly.

Still yet to drive it so cant be 100% sure, but already i know its different, as when i replace the plug the idles blips up slighty before dropping back down to idle Well chuffed.

 

 

another one solved

 

looks like im on free beer all nite next time im out cheers guys - glad to help.

this is EXACTLY what passionford is about